This invention relates to a system and apparatus for the disposal of solid waste materials and for the conversion of the combustible organic fraction of such solid waste materials to a useable fuel material. Recovery of a major portion of the inorganic fraction may also be accomplished.
The disposal of solid wastes has become an increasingly severe problem in view of the increasing population, the concentration of populations in urban and suburban areas and in the increasing number of industries generating solid wastes. A large fraction of such waste may be of organic origin which is of a combustible nature. This organic fraction is normally made up of such materials as paper, textiles, leather, rubber, yard wastes, wood, wood wastes and bark, garbage and some forms of plastics. However, such an organic fraction requires processing to make it suitable as a fuel. In addition, solid wastes generally contain an inorganic fraction which may comprise ferrous and nonferrous metals as well as glass, dirt, and other forms of plastics. The apparatus of this invention is directed to the disposal of solid wastes and to the recovery of the organic fraction of solid waste in the form of a finely divided product which can be used as a fuel or fuel supplement. Optionally, this apparatus may also include means to recover the various components making up the inorganic fraction in the form of one or more valuable products.
Inasmuch as it is becoming increasingly difficult to dispose of solid wastes by such previously used means as dumping and filling, a critical need has arisen to find other techniques for solid waste disposal, such techniques of necessity being those which do not create pollution problems and of preference those which do not require the expenditure of appreciable amounts of energy. Moreover, if the end product or products of the disposal process are themselves usable, the process is even more desirable.
In general, the techniques more recently proposed for solid waste disposal may be classed as those which provide apparatus for bulk reduction, conversion or reclamation. Although some advances in bulk reduction (densification) have been made, each of the techniques used (baling, incineration, etc.) have inherent drawbacks including disposal of the densified material, pollution control, and the like. Conversion is generally defined as the chemical or biochemical transformation of the waste material into a useful product; and the techniques used include pyrolysis (destructive distillation or decomposition at elevated temperatures, e.g., 750.degree.-1600.degree. F in the absence of air or other reactive or oxidizing gases), partial oxidation, composting (aerobic conversion of cellulose waste into inert humus-like material by aerobic bacteria), hydrogenation, wet oxidation, hydrolysis, anaerobic digestion, biological fractionation and the like.
Reclamation involves the separating out by handsorting materials such as glass, plastics, metals, papers, textiles and the like for reuse in one form or another. However, other than some forms of paper (corrugated and newsprint), some plastics and textiles, the combustible component of organic solid wastes has not been recovered. Only recently has any serious attempt been made to convert these combustible materials to a form in which they could be used as a fuel.
In copending applications Ser. Nos. 456,338 now U.S. Pat. No. 3,961,913 and 557,433 now U.S. Pat. No. 4,008,053 filed in the names of Richard S. Brenneman and John J. Clancy for "Process for Treating Organic Wastes and Product Thereof," and assigned to the same assignee as this application, there is described and claimed in a process which makes it possible to treat the combustible organic fraction of solid wastes to form a finely divided, relatively dense fuel or fuel supplement using a relatively small amount of energy. The resulting product is a finely divided material usable as a fuel or fuel supplement in existing combustion equipment without requiring any substantial modification. This product retains essentially all of the dry weight and caloric content of the original solid organic waste material from which it is formed.
In the process described in these copending applications, the combustible organic fraction of solid waste is treated with one or more mineral acids and heated to an elevated temperature under conditions to form an embrittled material, readily reducible to a finely divided form, without effecting any substantial pyrolysis, decomposition or loss in dry weight of the organic waste. The process may also include the steps of separating organic and inorganic fractions, primary gross size reduction and predrying before embrittlement and grinding, separating the fuel product from inorganics, pelletizing and mixing with other fuels subsequent to embrittlement. The apparatus of this invention is particularly suited for carrying out such a process.
It is therefore a primary object of this invention to provide apparatus, along with a system incorporating such apparatus, for disposing of solid waste materials containing both organic and inorganic fractions. It is another object of this invention to provide apparatus for waste disposal of the character described which includes the treating of the combustible organic fraction of the solid waste to embrittle it and form it into a fuel or fuel supplement. It is a further object of the invention to provide such apparatus which requires the expenditure of relatively little energy, which makes it possible to achieve a net energy efficiency (fraction of total contained energy in waste recovered) of as much as 0.75, and which provides the capability of being formed into a system which may be substantially self-contained as far as heat energy requirements are concerned.
A further object of this invention is to provide apparatus to convert the organic fraction of solid waste to a useable product having a bulk density which is greater than and handling characteristics which are materially improved over the original form of organic material in the wastes treated.
Still another object of this invention is the providing of apparatus for the disposal of solid wastes which results in the elimination or minimization of the need for land fill and which produces only sterile by-products in the form of gas and any solids residue which may result. A further object is to provide such apparatus which does not create any pollution control problems.
It is a yet further object of this invention to provide apparatus for separating the components of solid wastes in a manner to provide a combustible organic fuel or fuel supplement along with reuseable ferrous and nonferrous metals and glass.
It is yet another primary object of this invention to provide apparatus for forming a unique fuel or fuel supplement formed from a combustible fraction of solid wastes. It is a further object to provide a fuel of the character described which retains essentially all of the dry weight and caloric value, in a greatly densified form, of the organic material from which it was formed.
An additional primary object of this invention is to provide apparatus which may be integrated into a total system of solid waste disposal and which is sufficiently flexible to be readily suitable for handling solid municipal waste.
Other objects of the invention will in part be obvious and will in part be apparent hereinafter.